Due to advances in network technology, a residential Ethernet network has been developed and supplied so that a user can conveniently control products by connecting electronic home appliances through networks. The residential Ethernet network is a home network, which provides a network environment to allow amongst others for transmission of time-sensitive traffic, in other words high quality audio/video traffic on Ethernet networks. IEEE 802 is considering new standards for residential Ethernet networks.
In a residential Ethernet network, a network intermediate device is indispensable for relaying transmission of data frames between nodes. Specifically, an A/V bridge operates as a network intermediate device to relay A/V data frames. In the A/V data frame transmission, the time required for the relay process is important. In other words, in order for nodes to output A/V data while maintaining synchronization between video and audio data, audio data frames and video data frames must be received within a specified period of time. In particular, in a case of broadcasting live data, continuous transmission is required in order to prevent the broadcast from stopping and to minimize delays in the intermediate transmission. Generally, it is required that a delay in A/V traffic transmission between sources and destination nodes on a residential Ethernet network is less than 2 ms.
In a conventional network intermediate device, the frames are transmitted by a store-and-forward method or a cut-through switching method. In the store-and-forward method, a frame received from the network intermediate device is stored, and then errors for the entire frame are checked using a cyclic redundancy check (CRC) value contained at the end of the frame. If errors are not found, the frame is forwarded to the destination recorded in a frame header.
In the store-and-forward method, a frame can be stably transmitted, but there is a problem in that a delay in relaying a frame is increased because the transmission is delayed for the time required for storing the entire frame by the network intermediate device. Specifically, assuming that a frame of 64 bytes is relayed in a fast Ethernet environment, about 2 μs is required to receive, store, and check the header, verify the destination address in the header to decide the destination, and command forwarding to the destination. Receiving, storing and transmitting the entire frame by a forwarding command takes about 5.12 μs. As a result, the time required for relaying a frame of 64 bytes is about 7.12 μs. Additionally, assuming that a frame of about 1526 bytes is relayed, the time required for processing the header in the same manner as described above is 2 μs, but, the time taken from the storage to the transmission of the frame is greatly increased to 122.08 μs. As a result, the total time of 124.08 μs is required. A plurality of network intermediate devices may exist on a frame transmission path between sources and destinations. Therefore, there is a problem in that the time required for transmitting the entire frame can exceed 2 ms.
The cut-through switching method is a method for forwarding and receiving a frame at the same time without storing the frame, by verifying the destination address of the header as soon as the frame is received. In the cut-through switching method, the forwarding is performed rapidly so that the delay in relaying can be minimized. However, when errors are found in the header, and particularly, in a field where the destination address is recorded, there is a risk that the frame may be relayed through other networks. In other words, since the CRC value for checking for errors in the frame is located at the end of each frame, the errors in the frame cannot be checked in this situation. Accordingly, there is a problem in that errors may be propagated while relaying the frames.
Accordingly, there is a need for an improved network intermediate device and method for checking for errors and forwarding a frame.